The present invention relates to polymer-coated particulates suitable for use in subterranean operations such as gravel packing, frac-packing, and hydraulic fracturing.
Hydrocarbon-producing wells are often stimulated by hydraulic fracturing treatments. In hydraulic fracturing treatments, a viscous fracturing fluid is pumped into a producing zone at a rate and pressure such that the subterranean formation breaks down and one or more fractures are formed or extended in the zone. Particulate solids, such as graded sand, which are often referred to as “proppant” may be suspended in a portion of the fracturing fluid and then deposited in the fractures when the fracturing fluid is converted to a thin fluid to be returned to the surface. These particulates serve, among other things, to prevent the fractures from fully closing so that conductive channels are formed through which produced hydrocarbons may flow.
Hydrocarbon-producing wells may also undergo gravel packing treatments to, inter alia, reduce the migration of unconsolidated formation particulates into the well bore. In gravel packing operations, particulates, often referred to in the art as gravel, are suspended in a treatment fluid, which may be viscosified, and the treatment fluid is pumped into a well bore in which the gravel pack is to be placed. As the particulates are placed in or near the zone, the treatment fluid either is returned to the surface or leaks off into the subterranean zone. The resultant gravel pack acts as a filter to prevent the production of the formation solids with the produced fluids. Traditional gravel pack operations involve placing a gravel pack screen in the well bore and then packing the surrounding annulus between the screen and the well bore with gravel. The gravel pack screen is generally a filter assembly used to support and retain the gravel placed during the gravel pack operation. A wide range of sizes and screen configurations is available to suit the characteristics of a well bore, the production fluid, and any particulates in the subterranean formation.
In some situations, hydraulic fracturing and gravel packing operations may be combined into a single treatment. Such treatments are often referred to as “frac pack” operations. In some cases, the treatments are generally completed with a gravel pack screen assembly in place with the hydraulic fracturing treatment being pumped through the annular space between the casing and screen. In this situation, the hydraulic fracturing treatment ends in a screen-out condition, creating an annular gravel pack between the screen and casing. In other cases, the fracturing treatment may be performed prior to installing the screen and placing a gravel pack.
Particulates (such as proppant or gravel) used in subterranean operations are often coated with a resinous or polymeric material to facilitate consolidation of the particulates. In some cases, the coating may also be used to strengthen low-quality particulates. Creating such coated particulates generally involves using solvent methods that may pose health or environments risks. Moreover, many particulate coating technologies, such as epoxy resin solvent systems, are relatively expensive. Thus, between the potential environmental and health hazards posed by many of the particulate coating technologies and the exorbitant costs of some, known coating techniques are less than ideal for widespread use in subterranean operations.